Update to PG18

[JacobCoffee]

Is your feature request related to a problem? Please describe.

➜ kubectl -n postgres get pod psf-pythondotorg-pythondotorg-1 -o jsonpath='{.spec.containers[*].image}'
ghcr.io/cloudnative-pg/postgresql:15.8-bookworm⏎                                                   

Describe the solution you'd like

PG18

Basic Example

No response

Describe alternatives you've considered

No response

Drawbacks and Impact

No response

Additional context

No response